Electrical terminal assemblies are widely used and are manufactured on a large scale. Many of the terminal assemblies presently known to the art are difficult to assemble and require expensive machinery and excessive worker hours to manufacture, thereby increasing their overall cost. There is thus a need for terminal assemblies that are easy to assemble.
Furthermore, virtually all of the terminal assemblies currently known to the art are difficult to disassemble. As a result, when manufacturing defects arise, they cannot be easily remedied at the manufacturing site, and often result in the disposal of the entire unit. This increases waste on the manufacturing side, which is ultimately reflected in the cost of the manufactured goods. Furthermore, the repair costs for products incorporating such assemblies is elevated, since the repair is more time consuming and frequently results in broken parts. In addition, since terminal assemblies are expensive to manufacture, there is a significant salvage value in used terminal assemblies. That salvage value is significantly decreased, however, if the assembly is not easily removable from the device in which it is installed. There is thus a need for terminal assemblies that are easy to disassemble, and that can be easily removed from devices in which they are installed.
To date, various terminal assemblies have been proposed in the prior art. However, none of these terminals can be readily assembled and disassembled. For example, one common terminal assembly consists of a threaded bolt on which is mounted a heating element sandwiched between two ceramic plates. The assembly is secured together by a first set of lock nuts, one disposed on the outer surface of each ceramic plate. A second set of lock nuts is provided adjacent to the first set to secure lead wires to the threaded bolt. Since the assembly or disassembly of such a system requires the placement or displacement of four lock nuts for each terminal assembly, the correction of manufacturing defects, as well as repair and salvage operations, are uneconomical in large scale operations.
Some of the more recent terminal assemblies have been designed to facilitate assembly. For example, U.S. Pat. No. 4,182,928 (Murphy et al.) proposes a heating element terminal assembly having a tubular terminal which terminates on one end in a flat blade. The terminal is inserted, tubular portion first, into the central bore of a two-piece ceramic mount, so that a segment of the tubular portion extends from the opposite end of the mount. Since the width of the blade is greater than the diameter of the central bore, the terminal inserts only as far as the blade. The segment of tubular portion extending from the mount is then crimped at a point immediately adjacent to the mount, thereby holding the assembly together.
While terminal assemblies such as that shown in Murphy et al. have the advantage of being easier to assemble than some other prior art units, assemblies of this type are difficult to disassemble, since this requires that the tubular portion of the terminal be uncrimped. In actual practice, it is more cost effective to simply break the terminal assembly each time disassembly is required (as when the heating element needs to be replaced in a heater that incorporates such an assembly) rather than to attempt to disassemble it.
A further feature of many prior art terminal assemblies which contributes to their manufacturing cost is the interface between the terminal and the lead wire. In many prior art devices, such as that disclosed in Murphy et al., the terminal is provided with a tubular portion into which a lead wire is inserted. The tubular portion is then crimped around the lead wire. This operation requires precise alignment of the lead wire with the tubular portion, much like the threading of a needle, and is impractical and time consuming in large scale operations. There is thus a need for a terminal assembly which is equipped with attachment means for engaging a lead wire that makes for easy alignment of the lead wire and the attachment means.
Yet another factor which increases the manufacturing cost of prior art terminal assemblies is their excessive use of materials. Safety standards in the electronics industry require a minimum surface spacing between live electrical parts, such as heating element terminals, and bare metal mounting structures, such as terminal plates disposed between ceramic insulator elements. To date, prior art terminal assemblies, such as that shown in Murphy et al., have met this minimum surface spacing requirement by using insulating elements that are sufficiently long or sufficiently wide to meet the spacing requirements. Such an approach involves an inherent waste of materials. There is thus a need for a terminal assembly which meets the surface spacing requirement without wasting materials.